1. Field of the Invention
The present invention relates to a network relay device, a network, and a network maintenance and operation method. In particular, it relates to a network relay device, a network, and a network maintenance and operation method using Ethernet OAM.
2. Description of the Related Art
Ethernet developed as a local area network (LAN) technology is also used for broadband networks. In broadband networks, despite requiring the security of communications, there have been prepared few functions for network maintenance and operation for conventional Ethernet. Accordingly, an Ethernet operation, administration and maintenance (OAM) function has been specified in ITU-T Y.1731 and IEEE802.1ag.
Also, a technology is standardized in IEEE 802.1ah that uses an encapsulation method called MAC-in-MAC as a high reliability method for Ethernet to provide a large scale network. IEEE 802.1ah provider backbone bridging (PBB) networks are host backbone networks for tying IEEE 802.1ad provider bridging (PB) networks. The PBB networks are suitable for use in large scale networks, compared to the PB networks.
Conventionally, a maintenance domain level administration method is known that is for operation, maintenance and administration of a network by transmitting/receiving Ethernet OAM frames inclusive of maintenance domain levels between two communication devices through the network. This maintenance domain level administration method includes the steps of transmitting an Ethernet OAM frame to be transmitted from a first to a second communication device through the network, with an outer OAM header added thereto; causing the communication devices connected to the network to perform operation, maintenance and administration based on maintenance domain levels included in the outer OAM header; and causing the second communication device to eliminate the outer OAM header from the OAM frame received from the first communication device and transmit the OAM frame.
With the above construction, this maintenance domain level administration method allows operation, maintenance and administration with numerous maintenance domains within a network using Ethernet OAM frames.
Refer to JP-A-2008-167331, for example.
In the maintenance domain level administration method disclosed by JP-A-2008-167331, when transmitting/receiving Ethernet OAM frames between mutually different standard networks, however, the specified network relay device connected to the network relays or discards an OAM frame transmitted from a network relay device connected to a different standard network without being able to determine it as an OAM frame. Proper network maintenance and operation is therefore impossible.